Just as a sudden rain can flood dry, cracked soil, sometimes seriously parched skin can't effectively absorb even the richest moisturizer. According to La Mer—maker of one of the most superemollient creams on the planet—that's because dryness damages skin's moisture barrier and throws off its pH, handicapping not just its ability to maintain moisture but to absorb it. New Hydrating Infusion serum responds to changes in pH and skin temperature (both dryness indicators) throughout the day. Plus, hydrating skin before applying cream "is like premoistening a sponge," says Loretta Miraglia, La Mer's senior vice president of development and innovation. "It makes the moisturizer work better."